Post on 22-May-2015
transcript
SUMMARY OF SELECTED ACCIDENT MODELING PAPERS
ROSS APTED
TASKTo summarize a discuss the following journal articles and conference proceedings.
Papers compare accident modeling approaches in varying degrees of detail.
Understanding Accidents - From Root Causes to Performance Variability (Hollnagel, 2002)
Comparison of some selected methods for accident investigation (Sklet, 2003)
Models of accident causation and their application: Review and reappraisal (Lehto, 1991)
(Hollnagel, 2002)
UNDERSTANDING ACCIDENTS - FROM ROOT CAUSES TO PERFORMANCE VARIABILITY
BACKGROUND
Published in 2002 in the Proceedings of the 2002 IEEE 7th Conference on Human Factors and Power Plants.
Erik Hollnagel Department of Computer and Information Science, University of Linkoping, Sweden
Accidents Analysis and Accident Prevention
The variability of Human Performance
Modelling of Cognition
Developed FRAM and CREAM
AIM
To give an overview of the developments in accident modeling.
How these developments have effected accident analysis and prevention.
1. Summary and analysis of the general modeling approaches (Sequential, Epidemiological, Systemic).
2. The role of humans in the accident process(actions of humans, work mentally of humans).
Applies models to socio-
technical system sometimes.
STRUCTURE
Summary of modeling techniques
- Sequential
- Epidemiological
- Systemic
Comparison of approaches
Role of Humans in accidents
- actions of humans
- work mentality of humans
Conclusion
GENERAL MODELING APPROACHES -SEQUENTIAL
Ferry’s domino Model of accident causation (Ferry, 1988)
Accident Evolution and Barrier model (Svenson, 1991, 2001)
Analysis of sequential approach
DOMINO MODEL OF ACCIDENT CAUSATION
5 factors in the accident sequence
1. Social environment
Factors effect an individuals perception of risk
2. Fault of the person
Human error
3. Unsafe acts or environment
faulty equipment, hazards in the environment
4. Accident
5. Injury
(Ferry, 1988)
DOMINO MODEL OF ACCIDENT CAUSATION
Domino Diagram
Time
So
cial
en
viro
nm
ent
Fau
lt o
f th
e p
erso
n
Uns
afe
acts
or
envi
ronm
ent
Acc
iden
t
Inju
ry
ACCIDENT EVOLUTION AND BARRIER MODEL
Accidents are represented as sequences of events or barriers that failed.
Target what went wrong.
Leaves out other factors that may be import in the investigation
(Øien, 2001)
SUMMARY OF SEQUENTIAL APPROACH
Attractive:
Allows you to think in a casual sequence
Represent as a graph
Allows easy communication of findings
Limited:
Not powerful enough to model more complex systems.
GENERAL MODELING APPROACHES -EPIDEMIOLOGICAL
Accident is described as a disease.
Some factor that effects the accident occur right away while others are latent.
Takes into account that events can manifest over time
Swiss cheese Model (Reason, 1997)
SUMMARY OF EPIDEMIOLOGICAL APPROACH
Overcome Limitations:
Superior to sequential models as latent events can be taken into account.
More suited to modeling complex systems.
Lack of detail:
Allowed the idefaction of general events that occurred could not go deeper.
SUMMARY OF SYSTEMIC APPROACH
Accidents naturally emerge, they are expected to occur. As detailed In Perrow’s Normal Accidents.(Perrow, 1984)
Focus:
Systemic models focus on the characteristics of a systems as oppose to a series of events that cause the accident in the system.
Difficult but powerful:
Ideal for complex systems but hard to represent graphically.
COMPARISON OF APPROACHES
(Hollnagel, 2002)
Table comparing general approaches
Highlights:1. What the accident
model produces
2. How the product information can be used in accident prevention
COMPARISON OF APPROACHES
Sequential models – search for root-cause of event - event linked by cause effect - cause is found then accident is prevented.
Epidemiological models – Looks at factors that may manifest later
- Looks at barriers that can be re-enforced or created to prevent further accident
Systemic models – looks for unusual relationships. - Monitors variability in systems performance
- Variability can be good and bad allows the system to develop, but bad variably must be trapped.
COMPARISON OF APPROACHES-CONCLUSION
.
These models should be used in conjunction with each other for the
best results.
No one modeling approach is better
than the other.
Each modeling approach has its own strengths
ROLE OF HUMANS IN ACCIDENTS
Humans play a role a ever level in an accident not just the sharp end.
Everyone blunt end is someone else's sharp end.
Blunt end sharp end relationship (Hollnagel, 2002)
ACTIONS OF HUMANS
Humans actions are not black and white and can only be judge in hindsight.
People do what they think is right at the time.
Different degrees of ‘being right’ not just correct or fail.
(Amalberti, 1996)
ACTIONS OF HUMANS
Being right or worn does nor accurately show humans roles in accidents.
ACTIONS OF HUMANS
In the sequential model an element is either correct or has failed, but human actions are not like this
Human actions are better suited to the epidemiological model as it allows for latent conditions , it takes into account that action may contribute to accident over time.
The systemic model is built on the concept of variability and does not focus on failures. This is perfect for representing variability of human action.
WORK MENTALITY OF HUMANS
Efficiency-Thoroughness Trade-off (ETTO) Principle
Human performance must satisfy conflicting criteria.
Will try and meet task demand and be as thorough as believed necessary while still being as efficient as possible and not wasting effort.
Performance can only increase in a stable environment
RO-RO ferries
Normal performance
(Hollnagel, 2002)
CONCLUSION
“Normal performance and failures are emergent phenomena”
Neither can be attributed to a specific part of function of the system.
The adaptability of human work is the reason behind its efficacy and it failures.
(Hollnagel, 2002)
(Sklet, 2004)
COMPARISON OF SOME SELECTED METHODS FOR ACCIDENT INVESTIGATION
BACKGROUND
Published in 2003 in Journal of Hazardous Materials
Snorre SkletDepartment of Production and Quality Engineering Norwegian University of Science
and Technology, Norway
Risk Analysis and Risk Influence Modeling
Safety Barriers
Safety Management
Accident Investigation
Does a lot of work with the oil industry
AIM
To give a brief summary of highly recognized accident investigation methods developed over last decade .
To compare these selected methods to highlight there qualities and deficiencies.
1. Summary of the methods ) brief summary of each one, framework for comparison).
2. Comparison of methods(table, analysis of comparison).
STRUCTURE
Selected Methods
Framework of comparison
Results of comparison
Analysis of comparison
Conclusion
SELECTED METHODSEvents and causal factors charting and analysis.
Barrier analysis.
Change analysis.
Root cause analysis.
Fault tree analysis.
Influence diagram.
Event tree analysis.
Management and Oversight Risk Tree (MORT).
Systematic Cause Analysis Technique (SCAT).
Sequential Timed Events Plotting (STEP).
Man, Technology and Organisation (MTO)-analysis.
The Accident Evolution and Barrier Function (AEB) method.
TRIPOD.
Acci-Map.
methods are commonly used and widely acknowledge in academic and accident investigating community
No systemic methods compered
FRAMEWORK OF COMPARISON
Details Framework of comparison highlighting the strengths and weakness of each technique.
7 categories
Whether the methods give a graphical description of the event sequence or not?
Can give overview of events
Allows for clear communication
Easy to see broken link
To what degree the methods focus on safety barriers?
Analysis of protective elements in the the system
FRAMEWORK OF COMPARISON
The level of scope of the analysis.
Which levels of Rasmussen’s classification of sociotechnical systems (Rasmussen, 1997) does the method model.
(Rasmussen, 1997)
FRAMEWORK OF COMPARISON
What kind of accident models that has influenced the methods?
sequential model, epidemiological model, systemic model
Whether the different methods are inductive, deductive, morphological or non-system-oriented?
The way in which the method looks at the accident e.g. does reason from the general to the specific.
FRAMEWORK OF COMPARISON
Whether the different methods are primary or secondary methods?
Primary Method – Self contained, stand alone method.
Secondary Method – used in conjunction with other method to provide special input.
The need for education and training in order to use the methods.
Novice – no experience or training is needed.
Specialist – In between Novice and expert.
Expert – Formal education and training is needed.
RESULTS OF COMPARISON
(Sklet, 2004)
ANALYSIS OF THE COMPARISON
The strongest in terms of graphical representation is STEP as it does not use a single axis and can represent one – one or one - *
Scope of most methods focus on levels 1-4 of the sociotechnical systems
Identifying the casual factors or event paths is important.
CONCLUSION
Accidents do not have a single cause so the investigation should reflected this buy using multiple methods.
A graphical representation is key, as it allows easy communication of information.
There should be one person of every investigation team that has the knowledge of different accident modeling techniques so the right tools can be chosen for the job
REFERENCESAmalberti, R. (1996). La conduite des systkmes ri risques. Paris: PUF.
Department of Energy. (1999). DOE Workbook, Conducting Accident Investigations . Washington,: Department of Energy.
Ferry, T. (1988). Modern Accident Investigation and Analysis. Second Edition. New York: Wiley.
Høyland, A., & Rausand, M. (1994). System reliability Theory: Models and Statistical Methods. New York: Wiley.
Hollnagel, E. (2002). Understanding accidents-from root causes to performance variability. Human Factors and Power Plants, 2002. Proceedings of the 2002 IEEE 7th Conference on , (pp. 1 - 1-6 ).
Lehto, M. (1991). Models of accident causation and their application: Review and reappraisal. journal of engineering and technology management , 173.
Perrow, C. (1984). Normal Accidents: Living With High-Risk Technologies. New york: Basic books.
Rasmussen, J. (1997). Risk management in a dynamic society: a modelling problem. Safety Sci. , 183–213.
Reason, J. (1997). Managing the Risks of Organizational Accidents. Aldershot: Ashgate.
Sklet, S. (2003). Comparison of some selected methods for accident investigation. Journal of hazardous materials , 29-37.
Svenson, O. (2001). Accident and Incident Analysis Based on the Accident Evolution and Barrier Function ( AEB) Model. Cognition, Technology & Work , 42-52.
Svenson, O. (1991). The Accident Evolution and Barrier Function (AEB) Model Applied to Incident Analysis in the Processing Industries. Risk Analysis , 499–507.
Øien, K. (2001). Risk indicators as a tool for risk control. Reliability Engineering & System Safety , 129–145.